Location of current carrying faults in integrated circuits by magnetic force microscopy

In Integrated Circuits failure analysis excessive power supply current flowing into the IC is often used to indicate the presence of a faulty device. Location of these faulty devices can be problematic as the devices are often buried under several layers of conducting interconnect. By imaging the magnetic field produced by current flowing in an IC a faulty device can be located. In this paper we present experimental results on imaging current-carrying faults on integrated circuits using Magnetic force microscopy. We have experimentally determined that MFM is capable of measuring currents as small as 1 to 10 microampere on ICs in a 30 Hz bandwidth. We have carried out modeling calculations comparing the simulation results with experimental results using realistic MFM tip geometry. From these results we have devised a method to accurately locate the position of the internal current carrying faults from MFM images with micrometer uncertainty.